Freezer cylinder construction



Jan. 10, 1967 c sTOELTlNG 3,296,817

FREEZER CYLINDER CONSTRUCTION umw Filed .May 27, 1964 2 Sheetsfiheet 1 Cam. R. Sroeume.

An'oauev 1967 c. R. STOELTING 3,

FREEZER CYLINDER CONS TRUCT ION Filed May 27, 1964 I 2 SheetsSheet 2 FROM FREEIER (EwwoR Mom TO COMPRESSOR FROM COND SER 6. 2. \rwerhog CARL R. STOEUHNG:

BYTOQNEY United States Patent 3,296,817 FREEZER CYLINDER CONSTRUCTION Carl R. Stoelting, Kiel, Wis., assignor to Stoelting Brothers Company, Kiel, Wis., a corporation of Wisconsin Filed May 27, 1964, Ser. No. 370,564 Claims. (Cl. 62-225) This application relates to freezing cylinders of the type used in manufacture of frozen custard and the like. These freezing cylinders are known in the trade as soft serve freezers. The present invention relates to the construction of such freezers in such a way as to increase the eificiency thereof.

An object of the present invention is to provide a low resistance flow path between the inner and outer cylinders of a soft serve freezer so that the capacity for a given size compressor may be increased.

Another object of this invention is to provide a soft serve freezer of the type having spaced inner and outer cylinders between which the refrigerant flows with means for increasing the effective heat transfer area to thereby increase the efficiency of the freezer.

Still another object of the present invention is to construct the soft serve freezer inner and outer cylinders so as to provide a hermetic seal between the cylinders and the means spacing the cylinders.

Still another object is to provide means for increasing the sensitivity of the feeler bulb of a thermostatic switch and/ or expansion valve.

Soft serve freezers are customarily provided with an inner cylinder in which a lead screw is mounted to move the material to be frozen from one end of the cylinder to the other. The cylinder is cooled by refrigerant and in the present construction the freezer is provided with an outer cylinder having a shrink fit onto square or rectangular copper bar stock wound on the inner cylinder to provide the means for defining the flow path for the refrigerant. The pitch of the bar stock is increased from the refrigerant inlet to the outlet to allow for expansion of the refrigerant and thereby hold down the velocity of flow and, hence, hold down the friction loss. This, therefore, means that there is less pressure drop between the inlet and outlet and, therefore, a compressor of given size will have greater capacity. The square bar stock achieves good conductivity between the inner and outer cylinders to thereby effectively make the outer cylinder part of the heat transfer area and thereby increase the capacity of the cylinder.

In order to shrink the outer cylinder onto the inner cylinder it is first fabricated to provide a slight gap when the longitudinal seam edges are brought together. This gap may be in the neighborhood of of an inch. When the longitudinal seam is welded the heating of the outer cylinder and consequent shrinking will achieve a shrink fit onto the bar stock which defines, for all practical purposes, a leak-proof path for the refrigerant while additionally achieving good heat transfer between the bar stock and the cylinders.

A final feature of the invention is the provision on the outlet of the freezer refrigerant path of a longitudinal dent in the refrigerant tube to receive the feeler bulb of a thermostatic switch and/or expansion valve. This dent tends to conform to the exterior of the feeler bulb and thereby insures better heat sensitivity of the bulb. Finally a cross dent is placed in the refrigerant tube to cause turbulance at the point where the feeler bulb is placed and, again, this increases the response sensitivity of the thermostatic switch and/ or expansion valve.

Other objects and advantages will be pointed out in, or be apparent from, the specification and claims, as will Patented Jan. 10, 1967 "ice obvious modifications of the single embodiment shown in the drawings, in which:

FIG. 1 is an elevation of the freezer cylinder assembly with parts broken away to show further details of construction;

FIG. 2 is a detail view of the outlet tube of the refrigerant system;

FIGS. 3 and 4 are sections taken on lines 33 and 4-4 respectively, of FIG. 2', and

FIGS. 5 and 6 are before and after views taken on line 5-5 to show the manner in which the longitudinal seam is welded to also shrink the outer cylinder or jacket on the bar stock.

The soft serve freezer shown in the drawings has a cylindrical body 10 including an inner cylinder 12 and an outer cylinder 14. At the left end of FIG. 1 liquid would be fed into pipe 16 through the end plate 18 and the frozen confection, such as frozen custard or the like, would be pushed out the right end of the body through suitable discharge fittings. It will be appreciated that a screw type conveyor or auger is provided within the inner cylinder 12 to propel the contents from one end to the other (assisted by the pressure feed of the contents) and to also scrape the frozen mix from the inner surface of cylinder 12.

In order to freeze the contents the refrigerant will pass over the outer surface of the inner cylinder 12. This refrigerant passes in the space between the two cylinders 12 and 14. In order to space the inner and outer cylinders one end of a piece of square copper bar stock 20 is welded to the cylinder 22 with the cylinder 12 installed in an engine lathe. Now, then, while the copper tube is held very tight the inner cylinder is turned in the lathe with the lathe lead screw determining the pitch of the wrap of the bar stock on the cylinder. This pitch is changed periodically as the bar stock progresses down the length of the cylinder, going from right to left, so that the pitch is increased to provide greater space between the flights of the bar stock as it goes from the inlet to outlet end. The left end of the bar stock is then terminated at 24 but need not be welded. The outer cylinder is then fitted over the bar stock 20 and when the outer cylinder is mounted on this assembly it spans the space between the back or rear plate 26 and the front plate 28 and closely fits on the bar stock 20. When initially mounted there will be about of an inch gap between the longitudinal seam edges as shown in FIG. 5. When this is welded, however, this will result in pulling the seam edges together, as shown in FIG. 6, to shrink the outer cylinder on the inner cylinder and thereby achieve what for all practical purposes is a leak-proof or hermetic seal between the outer cylinder and the bar stock. This has proven to be a very successful method of fabrication which does not involve great expense. At the right-hand end of the cylinder assembly a refrigerant inlet tube 30 is fitted and at the left-hand end the outlet tube 32 is fitted. Therefore, refrigerant enters at the right and progresses in a spiral fashion down the length of the cylinder assembly and exits through tube 32.

As the refrigerant passes from the inlet to the outlet it is provided with an increasing flow path in the sense of cross-sectional area and this accommodates the increase in volume as the refrigerant boils going through the cylinder assembly. Since the refrigerant flow path accommodates the increasing volume of the refrigerant the rate of flow is not unduly increased and, therefore, the frictional losses are held to a minimum. This results in a low pressure drop from inlet to outlet with the result that a given size compressor can, in effect, deliver a greater amount of refrigerant.

Another factor contributing to high efficiency in the present arrangement is the provision of the square copper bar stock between the inner and outer cylinders. Copper, of course, has high thermal conductivity and since square stock is used it has a good contact area with respect to the inner and the outer cylinders. Therefore, heat can readily flow from the inner cylinder through the bar stock to the outer cylinder and, therefore, the outer cylinder becomes an important factor in achieving heat transfer. This greatly increases the efficiency of the freezer as has been demonstrated by substituting round stock for the square stock with an appreciable fall off in efliciency for an otherwise identical freezer assembly.

To further enhance the response and efiiciency of the present freezer the outlet tube 32 is provided with longitudinal dent 34 which is formed to receive the feeler bulb 36 of the thermostatic expansion valve 38. It will be appreciated the feeler bulb and the thermostatic expansion valve are connected by the usual capillary tube 40 and, as is well known, the thermostatic expansion valve regulates flow of refrigerant into the freezer (which is the equivalent of an evaporator in the usual refrigeration system) in accordance with the temperature of the gases flowing out of the freezer. Therefore, by providing the longitudinal dent 34 in the outlet tube and by forming this dent to receive a substantial surface of the feeler bulb the response of the feeler bulb can be greatly increased. Furthermore, the tube is provided with a transverse dent 42 which will occasion turbulent flow of the gases flowing past the feeler bulb. This will also render the bulb more sensitive to temperature conditions at the freezer outlet.

Instead of valve 38 a switch can be employed. This would be the on-ofif switch of the system. The same advantages follow in such a use.

Since the present freezer has appreciably increased efficiency and response characteristics the refrigeration system used in connection with this freezer can be smaller for the same size capacity freezer than has been customary heretofore or, put another way, a given size refrigeration system used in conjunction with the present freezer assembly will result in a freezer having greater capacity than has been possible heretofore.

Although but a single embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

I claim:

1. In a soft serve freezer, the combination of inner and outer cylinders, a rectangular spacer of bar stock having high thermal conductivity wound on the inner cylinder and having contact with the outer cylinder to define a spiral flow path around the length of the cylinders, a refrigerant inlet to the spiral flow path at one end of the freezer, and a refrigerant outlet from the spiral flow path at the other end of the freezer, the pitch of the spacer winding increasing from the inlet to the outlet end.

2. The construction according to claim 1 in which the outlet tube is provided with a longitudinal dent curved to receive the feeler bulb of a thermostatic control device and further including a transverse dent adjacent the longitudinal dent for increasing turbulence in the tube adjacent the feeler bulb.

3. In a refrigerating system, a tube, a thermostatic control device including a feeler bulb, a longitudinal dent in the tube receiving the bulb therein, and a transverse dent in the tube adjacent the longitudinal dent to in crease turbulence.

4. In a refrigerating system, a tube, a thermostatic control device including a feeler bulb, said bulb being mounted on the tube, and a transverse dent in the tube adjacent the bulb to increase turbulence in the tube.

5. In a freezer, an inner cylinder, a spacer of rectangular cross section and high thermal conductivity wound on the cylinder in spiral fashion, an outer cylinder fitting snugly over the outer periphery of the spacer whereby a spiral flow path is defined, a refrigerant inlet to said path at one end and a refrigerant outlet at the other end, the pitch of the spacer winding increasing from inlet to outlet.

References Cited by the Examiner UNITED STATES PATENTS 1,694,532 12/1928 Dennison -165 1,969,652 8/ 1934 Larkin. 1,987,341 1/1935 Kachel 29447 2,035,213 3/1936 Anderson 165156 2,190,384 2/1940 Newman 73-343.2 2,231,163 2/1941 Johnson 62-225 X 2,356,779 8/ 1944 Morrison 62-45 1 2,412,271 12/1946 Kercher 29-4-47 2,449,343 9/ 1948 Torbensen 6245 1 FOREIGN PATENTS 21,821 10/ 1905 Austria. 88,617 2/ 1960 Denmark.

MEYER PERLIN, Primary Examiner. 

3. IN A REFRIGERATING SYSTEM, A TUBE, A THERMOSTATIC CONTROL DEVICE INCLUDING A FEELER BULB, A LONGITUDINAL DENT IN THE TUBE RECEIVING THE BULB THEREIN, AND A TRANSVERSE DENT IN THE TUBE ADJACENT THE LONGITUDINAL DENT TO INCREASE TURBULENCE. 